From 854326a0ba803161bb57db9cc7e1b375595befef Mon Sep 17 00:00:00 2001
From: Jean-Francois Dockes <jf@dockes.org>
Date: Tue, 6 Aug 2019 16:31:59 +0200
Subject: [PATCH] renameormove: Windows: unlink existing file before rename

---
 src/utils/copyfile.cpp | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/utils/copyfile.cpp b/src/utils/copyfile.cpp
index 2b8e1123..8972ba3f 100644
--- a/src/utils/copyfile.cpp
+++ b/src/utils/copyfile.cpp
@@ -129,6 +129,13 @@ out:
 
 bool renameormove(const char *src, const char *dst, string &reason)
 {
+#ifdef _WIN32
+    // Windows refuses to rename to an existing file. It appears that
+    // there are workarounds (See MoveFile, MoveFileTransacted), but
+    // anyway we are not expecting atomicity here.
+    unlink(dst);
+#endif
+    
     // First try rename(2). If this succeeds we're done. If this fails
     // with EXDEV, try to copy. Unix really should have a library function
     // for this.